1. Field of the Invention
The present invention relates to a liquid drop ejection head and an image forming apparatus.
2. Discussion of the Background Art
In general, an image forming apparatus, such as a printer, a fax, a copier, a plotter, a multifunction machine combining these functions, etc., sometimes includes a print head having a liquid drop ejection head for ejecting ink drop and executes image formation by adhering the ink drop to a sheet, such as a recordation medium, a transfer member, etc., while conveying the sheet.
Specifically, the image forming apparatus can execute the image formation by ejecting liquid drop onto a medium, such as paper, textile thread, texture, cloth, leaser, metal, plastic, glass, wood, ceramics, etc. The image formation provides the medium with not only an image having meaning, such as character, figure, etc., but also a meaningless image, such as a pattern etc. The ink includes wide range of material as far as it can become a liquid state, such as DNA test piece, registration, pattern material, etc., when ejected.
In such an image forming apparatus, as an image processing device, such as a personal computer etc., progresses, a printing speed increases while improving a quality of an image. To achieve the high-speed printing, the print head is elongated by increasingly employing a number of nozzles or is made in a line state connecting plural heads.
Further, as one of attempts to obtain the high quality image, a multiple nozzle headline is employed to use many ink colors. Thus, in comparison with the conventional one, a printing apparatus mounting such a print head becomes bulky and expensive. Accordingly, a printing head or a carriage mounting the print head are demanded to be more downsized at low cost.
A flexible printed circuit (FPC) board is utilized to provide an electric signal such as printing information from a printing apparatus body side to a printing head.
In the past, as shown in the Japanese Patent Application Laid Open No. 2002-046256, a flexible printed circuit board is arranged at both side surfaces of a nozzle of a printing head, and one ends of the flexible printed circuit boards are connected to an actuator of the printing head with the other ends being connected to a connecter electrically connected to a printing apparatus body side.
The Japanese Patent Application Laid Open No. 2002-090481 describes that two lines of drive elements are provided, while two drive circuit boards of the same shape are arranged thereto respectively on the same side of those.
Further, the Japanese Patent Application Laid Open No. 2002-321371 provides a flexible printed circuit board with its connection sections connecting to a printing head. Specifically, the flexible printed circuit board is perpendicularly bent in a lengthwise direction between the printing head and a drive circuit board to be folded back by the angle of 180 degree so that the connection sections are arranged opposing each other.
However, since the connecting parts are similarly arranged opposing to each other on both sides of the nozzle as the flexible printed circuit boards in the conventional art of the Japanese Patent Application Laid Open No. 2002-046256, the printing head cannot be thinned.
Further, since the drive circuit board needs two sheets of the flexible printed circuit boards, a number of parts and accordingly the cost, increases in the conventional art of the Japanese Patent Application Laid Open No. 2002-090481. When it is attempted to use only one sheet of the drive circuit board, since input terminals to two sheets of the flexible printed circuit boards are arranged opposing each other via the drive circuit board, wiring is overcrowded on the drive circuit board, and a stacking number of layer of the drive circuit boards unavoidably increases. As a result, cost of the board increases.
As described in the Japanese Patent Application Laid Open No. 2002-321371, even though part cost is decreased by folding back the common part of the flexible printed circuit board, the carriage with the printing head is insufficiently downsized, and the part cost is insufficiently reduced.
Further, as illustrated in FIG. 25, when a line type head unit 1000 of a line type image forming apparatus includes plural short heads being staggered and held by a head supporting member 1002, the head unit 1000, and accordingly the apparatus as a whole become extraordinary bulky. The length L of the head unit 1000 depends on a size of a printing medium used in an apparatus. However, the width W of the head unit 1000 does not depend on the size and directly affects the size of the entire apparatus. Since the width per head 1001 is w, the total width W of the head unit 1000 amounts to 2×w. Thus, decreasing the width w per head 1001 means decreasing the head unit 1000.
Thus, it is important and thus is demanded to decrease the width of the head unit for downsizing the line type apparatus body. A serial type printing head has the same demand. Because, when a printing head is wide, a scanning range of a carriage is also wide, so that downsizing and high-speed printing of the apparatus cannot be promoted.